Angiography is a procedure used in the treatment of cardiovascular conditions including abnormalities or restrictions in blood vessels towards, the network of passageways through which blood travels in a human or animal body. During angiography, a radiographic contrast material is injected through a catheter into a vein or artery, which then passes to vascular structures in fluid communication with the vein or artery. When X-rays are passed through the region of the body into which the material is injected, they are absorbed by the contrast material, providing radiographic images of the desired vascular structure(s). The images can be recorded on film or video tape and/or displayed on a fluoroscope monitor. The images can be used for many purposes, as for example, diagnostics and for operative procedures such as angioplasty, wherein a balloon is inserted into a vascular system and inflated to open a stenosis.
The contrast material can be injected into the catheter by either manual or automated injection systems. While the apparatus for injecting the contrast material can vary, most current systems include a syringe operatively connected with the catheter. The syringe has a chamber for holding the contrast material and a plunger reciprocally moveable within the chamber. The contrast material is suctioned into the chamber when the plunger is moved to create a partial vacuum within the chamber. A reversal of the plunger direction first forces air out of the chamber and then delivers the contrast material to the catheter at a rate and volume determined by the speed of movement of the plunger.
In a manual system the user or operator loads the syringe and ejects air from the chamber before connecting the syringe to the catheter. The user of a manual system adjusts the rate and volume of injection by altering the manual force applied to the plunger. The maximum injection pressure for manual systems is typically limited to 150 p.s.i. (i.e. the maximum pressure that can be applied by the human hand), and the maximum quantity of fluid is about 12 cc. Such manual systems typically do not accommodate any safety features such as the restriction or prevention of injections outside of predetermined injection parameters (such as rate or pressure), and generally do not include active sensors or alarms to detect air bubbles or other hazards.
Angiography can include the injection of fluids other than the contrast material. For example, a saline flush and/or the injection of fluid medications may be desired. One of the most commonly used manual injection systems includes a valve mechanism having a plurality of manually activated valves that the operator selectively opens and closes to direct flow of the desired fluids into or out of fluid channels connected to the syringe or catheter. When the operator aspirates or injects the contrast fluid into or out of the syringe chamber, the fluid flows through the path of least resistance as directed by the relative positions of the valves. When changing the valve positions, one or more fluids may be selectively injected.
A number of motorized and automated injection systems have appeared in the art, to address the limitations and dangers associated with the manual injection systems. Most such automated systems use a syringe with a linear actuator whose movement is regulated by an electronically controlled motor. For a description of such typical systems, the reader is referred to U.S. Pat. No. 4,812,724 issued on Mar. 14, 1989 and to U.S. Pat. No. 4,854,324 issued on Aug. 8, 1989. Such automated injection systems are generally fixed rate injection systems, wherein an operator enters a parameter representing the desired fixed volume of contrast material and the desired fixed rate of injection into the system. Such systems typically include an initial specified rate of flow increase leading to a final rate of injection, until the entire volume of contrast material is injected. There is no interactive control between the operator and the system, except to start or stop the injection. Any change of flow rate must occur by stopping the injector and resetting the parameters. The automated nature of such machines, however, offers the addition of injection speed and volume limit control features that were not available with the earlier manual injection systems.
Since the optimal flow rate can vary considerably between patients, the lack of ability of such prior art systems to vary the rate of injection during an injection procedure can result in suboptimal quality of angiographic studies. In cardiovascular systems, the rate and volume of contrast injection depends on the volume and flow rate within the blood vessel or other cardiovascular chamber being injected. In many or most cases, these parameters are not known precisely and can change rapidly during the injection procedure as the patient's cardiovascular system conditions change in response to such things as, for example, drugs, illness or normal physiology. Consequently, the initially selected volume or flow rate parameters for an injection of contrast material may be insufficient to outline a desired structure on an X-ray image, thereby necessitating another injection. Conversely, an excessive flow rate may injure the cardiovascular vessel being injected, cause the catheter to be displaced relative to the patent or lead to toxic effects (such as abnormal heart rhythm) from contrast material overdose. Our prior cross-referenced applications, hereby fully incorporated by reference, address the prior art's lack of ability to vary the injection parameters during an injection procedure.
While the prior automated systems have significantly improved the accuracy and reliability of angiography injection procedures, the known systems have not been as user friendly as desired, have not had automated capability to determine default injection parameters unique to the physiology or other values of the patent to be treated, and have not incorporated pro-active safety features in their system designs.
All automated systems necessarily require some type start-up procedure to be conducted prior to initializing an injection procedure with the system on a patient. Heretofore, such automated systems have not been particularly user friendly, but have required the operator or set-up technicians using the system to follow a set-up setup and initialization procedure according to instructions in a user manual. Besides the nuisance factor associated with the care and handling of such manuals, it is possible to mistake a manual of one injector with that of another or to use an outdated manual that does not include the most current initialization procedures and/or parameters. A further shortcoming of prior automated systems is that such systems do not maintain and display to the operator the actual real-time injection parameters existing at any instant of the injection procedure, or the cumulative amount of contrast material that has been administered to a patient from the beginning of the injection procedure, to the present. Heretofore, accumulating and maintaining a record of such cumulative information for an injection procedure has been a responsibility of the operator.
Known automated injection systems typically require entry of the following injection parameters: the volume of contrast material to be injected, the flow rate of injection, the maximum permitted injection pressure and the rate of change of injection flow rate (i.e. the rise time). Since the three parameters of flow, volume and duration are related, if any two are known, the third can be calculated. Known systems either require the operator to determine the desired parameters for an injection procedure, or allow the operator to recall parameters that the operator has stored in the system's memory from a prior procedure. Some injection systems also include stored default settings for the parameters associated with different types of injection procedures that can be used by the operator. A deficiency of such prior systems, however, is that such default and stored parameter values are arbitrarily determined and are not generally determined using unique properties or values or characteristics of the patient being treated.
Known automated injection systems also have not incorporated pro-active safety features in their system designs. While a microprocessor has been used in prior systems for providing primary automated control of the syringe plunger movement, back-up safety systems for checking on the multiprocessor's effectiveness have not been of a pro-active nature, but have been of a type that simply have the capability of interrupting or stopping an injection if the safety system determined that the injection procedure is being performed outside of one or more of the predetermined injection parameters. The present invention addresses these and other deficiencies of known automated angiographic injection systems.